Process crust trimmings in a food processor or blender until fine and use for other casserole toppers.
Dry bread cubes in a 300°F. oven for 8 to 10 minutes; cool. After transferring mixture to baking dish, cover with foil and chill up to 24 hours. Bake in the 350°F. oven for 40 minutes; uncover. Top with cheese and bake, uncovered, for 25 minutes more or until puffed and set. Let stand as above.